Hi FScalini (FScalini), in <4dcce472.352e9d9c@aol.com> on Apr 10 you wrote:

> Several times throughout your PIC book, I noticed  "& 0x07F".  For example,
> pages 222 and 223:
>    clrf TRISB & 0x07F
>    ...
>    ...
>    movwf OPTION_REG & 0x07F
>
> If it is an address, what is the significance of it?  Thanks.

OPTION_REG & 0x7f (or 0x07f) is an AND mask.  The result of this expression
is OPTION_REG with highest bit clear.

The PIC has registers in several banks.  You have to select a bank in the
STATUS register.  When you access a register (such as TRISB or OPTION_REG)
that is not located in bank 0 (the default bank), the assembler generates a
warning - to remind you that you need to set the bank bits correctly in
your code.  Otherwise an access to TRISB would end up in PORTB for example,
because PORTB is at the same location in bank 0 as TRISB is in bank 1.

Probably the author of the code snippets above did set the bank bits
accordingly, and did want to suppress the warning associated with the
access (because he has checked it already).  Therefore he cuts off the MSB,
that indicates its an access to bank 1 to the assembler.

When there are still warnings they show sections of the code that he FORGOT
to treat this way, and that's how warnings should be like.